Field of the Invention
The present invention relates to a mold, an imprint apparatus, and a method of manufacturing an article.
Description of the Related Art
An imprint technique forms a pattern by curing an imprint material by ultraviolet light or heat while pressing a mold having the pattern formed on it against a substrate applied with the imprint material. This imprint technique eliminates the need for an expensive apparatus such as a projection lens in photolithography and allows micropatterning by a simple apparatus.
In the imprint technique, if an air space remains between a mold and an imprint material on a substrate when pressing (imprinting) the mold against the imprint material, it is impossible to fill a mold pattern portion with the imprint material, thereby generating a defect in a pattern.
To prevent an air space, there is known a technique of performing imprinting by filling an imprint space with a gas such as helium which penetrates an imprint material, and applying pressure to the back surface of the mold to deform a mold pattern portion into a downwardly convex shape (US Patent Application Publication No. 2008/0160129). According to this technique, at the time of imprinting, it is possible to fill the mold pattern portion with the imprint material without leaving any air space by bringing the mold into contact with the imprint material from the central portion of the mold pattern, and moving the mold so as to expel gas outside the pattern.
When separating (releasing) the mold from the imprint material after curing the imprint material, the adhesion strength changes depending on the pattern density, and thus the mold release speed suddenly changes. This change may cause a fall of the pattern. In Japanese Patent Laid-Open No. 2010-221374, a sudden change in mold release force or mold release speed is suppressed by increasing/decreasing the amount of pressure applied to the back surface of the mold at the moment of mold releasing in accordance with the high density of the pattern.
As described above, as an imprint technique, there are provided an imprint method and a mold shape for deforming a pattern portion into a downwardly convex shape by applying pressure to the back surface of a mold at the time of imprinting and mold releasing.
When a pattern surface is deformed into a downwardly convex shape and impressed by applying pressure to the back surface of a mold, the timing at which the pattern surface is brought into contact with an imprint material is later toward the outer side of the pattern. In this case, since the contours of the downwardly convex deformed shape of the mold are circular while the pattern region has a rectangular shape, the timing at which the four corner portions farthest from the center of the pattern are brought into contact with the imprint material is particularly late. Therefore, the productivity may decrease due to a delay in a filling time, or an unfilling defect depending on the locations of the four corner positions may be generated.
When releasing the mold after curing the imprint material, the mold release force is reduced and a change in mold release speed is suppressed by applying pressure to the back surface of the mold to deform the mold into a circular convex shape, as in Japanese Patent Laid-Open No. 2010-221374. Similarly to imprinting, however, since the circular convex shape of the mold is different from the rectangular shape of the pattern region, it is impossible to maximize the effect, and it is difficult to reduce the mold release force and to control the mold release speed.
Consequently, as for the present imprinting, and the deformed shape of the mold in mold releasing, the productivity may decrease or the mold may be damaged due to a pattern defect such as unfilling or a fall of the pattern, or a delay in the filling time.